The TtlCalc2 project is a recreation of the original (now TtlCalc1) project from 2005 that implemented a four-function floating point calculator in TTL logic without a microprocessor.
This version uses multilayer PCBs and Nixie tube and neon indicators for the display, whereas the original used wire wrap boards and LED 7-segment displays. Both versions share the same architecture, with separate (Harvard architecture) 8-bit data and 12-bit instruction address spaces, a 4-bit data path, and a 16-bit instruction word.
The goal of the original was to gain experience designing and implementing a processor with these techniques with an eye towards taking on the design of a more capable minicomputer.
This repository contains the hardware and software components for the TtlCalc2 project, including simulation tools, assembly code, and documentation.
hw/: KiCad schematic and PCB designs for the hardwaresw/: Software for the calculator (microinstruction ROMs)doc/: Design and implementation documentationTtlCalcSim/: Simulator for the calculator hardware
The hw directory contains KiCad project files for the TtlCalc2 hardware design.
ttlcalc2/: Logic board hardware design files.ttlcalc2_display/: Display driver module design files.ttlcalc2_front/: Front panel design files.
TODO: The keyboard and keyboard interface still needs to be designed.
The hw/ttlcalc2/gerbers directory contains the Gerber files for PCB manufacturing.
The sw directory contains assembly code for the TtlCalc2 project. This project uses the customasm assembler to generate the microcode stream.
ttlcalc2.asm: Mnemonic definitions for the TtlCalc2 microcode.fib.asm: Assembly code for calculating Fibonacci numbers.
TODO: Port original ttlcalc assembly source code to new customasm syntax.
For example, to build the Fibonacci code, run:
customasm fib.asmThis generates fib.bin which you can then load into the simulator and run.
The doc directory contains documentation for the TtlCalc2 project.
The TtlCalcSim directory contains the simulation tools for the TtlCalc2 project. The simulator is implemented as a C#/.NET 9.0 console application.
TtlCalcSim/: Core simulation library.TtlCalcSim.ConsoleUI/: Console-based user interface for the simulator.TtlCalcSim.Tests/: Unit tests for the simulation library.
To build the simulator, open the TtlCalcSim.sln solution file in Visual Studio and build the project, or use the following command from the TtlCalcSim directory:
dotnet buildTo run the unit tests, use the following command from the TtlCalcSim directory:
dotnet testEither run the simulator executable after building, or run it via the dotnet command:
dotnet run --project TtlCalcSim.ConsoleUIThis project is licensed under the MIT License. See the LICENSE file for details.